Saturday, January 9, 2010

Furnace intake clogged by ice crystals during extremely cold week

Board placed to discourage floating ice crystals from entering intake pipe.
You can see moisture freezing onto those plant stems. Temp is below 10F

Warm exhaust makes a bare spot on the ground below.

Moisture freezing on the bush to the right which is over 10 ft away. sort of like hoar frost.

Picture with furnace running so you can see the steam.

In windless condition, the steam goes everywhere. Tends to flow right because the AC blocks the left side.

Added another shroud over the intake pipe. This might decrease the number of ice crystals entering the intake without restricting the air flow. Plus when there is a blizzard coming from the right side, less snow will enter the intake opening.
I might try a length of black perforated drain pipe, maybe 4 ft. That would create a protected zone to suck air from. Unrestricted, but decrease the number of ice crystals and snow entering the intake opening. The black pipe might get heated by sunshine and help evaporate snow and ice that gets into the pipe.


  1. have the same problem as the pipes in my house sit about 18" above the ground, currently I'm shoveling around them to keep things running.

    As goofy as it may look you may want to grab some wood scraps and make a box to sit around/on top of the pipes. I'd make the top solid (to prevent the snow from going through, and put angled slats on the side with good sized gaps for airflow. As long as the box is taller than the snow it should still be able to breathe sufficiently.


    Try to figure out a way to deflect air around the intake. I doubt that it's sucking the snow from the ground, I think that it's sucking the snow in when it's windy. If you just box it or put a sheet of wood / plastic in a key location to deflect wind it might be enough to take care of the problem.

    Great insight! I couldn't point my intake vent in another direction, but I bought a slinky-type vent hose, clamped it around the neck of the intake vent, and routed the other end a good 3 feet away from the exhaust vent

    This seems (fingers crossed) to have fixed my problem.

    In my case, it definitely seemed as though the hot humid air from the exhaust vent was being sucked back into the intake vent, eventually condensing, turning to ice, and blocking the airway.

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